Folds, Faults and Other Records of Deformation

Significance to CCS Fundamental to trapping configuration Fundamental to trapping configuration Important for caprock integrity Important for caprock integrity

Stress Force per unit area Force per unit area Compression Compression Tension (rare) Tension (rare) Shearing Shearing

Or, principal compressive stress vertical

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks)

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks) Ductile: plastic deformation, no fractures Ductile: plastic deformation, no fractures

Folded gneiss and marble

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks) Ductile: plastic deformation, no fractures Ductile: plastic deformation, no fractures Brittle favored by: Brittle favored by:

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks) Ductile: plastic deformation, no fractures Ductile: plastic deformation, no fractures Brittle favored by: Brittle favored by: low temperatures low temperatures

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks) Ductile: plastic deformation, no fractures Ductile: plastic deformation, no fractures Brittle favored by: Brittle favored by: low temperatures low temperatures low confining pressures low confining pressures

Undeformed Low confining pressure High confining pressure

Brittle Versus Ductile Deformation Brittle: material fractures (breaks) Brittle: material fractures (breaks) Ductile: plastic deformation, no fractures Ductile: plastic deformation, no fractures Brittle favored by: Brittle favored by: low temperatures low temperatures low confining pressures low confining pressures high strain rates high strain rates Rock type Rock type

Brittle diabase, ductile marble

Mapping Geologic Structures Strike Strike Dip Dip

Mapping Geologic Structures Strike Strike Dip Dip Constructing cross sections Constructing cross sections

Folds Bending of rocks, often as a result of compression

Anticlines and Synclines

Raplee anticline and San Juan river, Utah

Limbs, axial planes, fold axes

Plunge

Plunging folds near Harrisburg, PA

Plunging anticline, SW Montana

Symmetrical, Asymmetrical, Overturned Limbs of equal length Limbs of unequal length

Overturned (almost?) anticline

Structural domes and basins

Faults and Joints Fractures in rock

Joints No visible displacement No visible displacement Types Types Unloading (exfoliation) Unloading (exfoliation)

Unloading joint, Yosemite NP, CA

Joints No visible displacement No visible displacement Types Types Unloading (exfoliation) Unloading (exfoliation) Cooling joints Cooling joints

Devil’s Postpile, CA

Devil’s Tower, WY

Joints No visible displacement No visible displacement Types Types Unloading (exfoliation) Unloading (exfoliation) Cooling joints Cooling joints Regional (tectonic) joints Regional (tectonic) joints

Joints in Navajo Sandstone, Arches NP, UT

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall Dip-slip faults Dip-slip faults Normal Normal

Normal fault, UT

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall Dip-slip faults Dip-slip faults Normal Normal Reverse Reverse

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall Dip-slip faults Dip-slip faults Normal Normal Reverse Reverse Thrust Thrust

Thrust: reverse motion with fault plane dipping <45°

Chief Mountain Klippe, Montana

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall Dip-slip faults Dip-slip faults Normal Normal Reverse Reverse Thrust Thrust Strike-slip faults Strike-slip faults Left lateral Left lateral Right lateral Right lateral

Faults Visible displacement Visible displacement Hanging wall and footwall Hanging wall and footwall Dip-slip faults Dip-slip faults Normal Normal Reverse Reverse Thrust Thrust Strike-slip faults Strike-slip faults Left lateral Left lateral Right lateral Right lateral Oblique-slip faults Oblique-slip faults

Rocks/textures created by faulting Fault breccia (visible angular fragments) Fault breccia (visible angular fragments) Fault gouge (incohesive, fine powder) Fault gouge (incohesive, fine powder) Mylonites (ductile flow/recrystallization) Mylonites (ductile flow/recrystallization) Pseudotachylites (frictional melting) Pseudotachylites (frictional melting)

Fault gouge

Mylonite

Pseudotachylite

Features associated with fault planes Slickensides (grooves or striations) Slickensides (grooves or striations) "Drag" folds "Drag" folds

Horsts, grabens, and rifts

Wildrose graben, Panamint Valley, southern California

Structural Traps for Hydrocarbons and CO 2 Fault traps Fault traps Fold traps

Lander Dome oil field, Wind River Basin, Wyoming

Structure Photos….

Joints in Navajo Sandstone, Arches NP, UT

1964 Alaska (M 9.2) Hanning Bay fault scarp on Montague Island. Vertical displacement feet. (USGS photo)